Use of turbochargers is known for internal combustion engines. A turbocharger includes a turbine connected to an exhaust system of an engine. Energy from the exhaust gas of the engine is used to power a turbine wheel within the turbine housing. The turbine wheel rotates a turbine shaft mounted in a center housing of the turbocharger between the turbine housing and a compressor housing. The turbine shaft is connected to a compressor wheel enclosed in the compressor housing, and is used to compress the incoming air of the engine.
Turbocharger shafts may reach rotation speeds of 270,000 revolutions per minute (RPM) or higher during operation of the engine. Due to the high rotational speeds of the turbine shaft, bearings are used to reduce friction of the turbine shaft and increase the service life of the turbocharger. Some turbine shaft bearings include ball bearings for severe applications, for example in racing engines, but most bearings are hydrodynamic bearings. In a hydrodynamic bearing, two cylindrical surfaces are in close proximity in the presence of a liquid. One of the two surfaces is static, and the other is attached to a rotating shaft, in this case, the turbine shaft.
In the case of an internal combustion engine, the fluid used to lubricate and operate the hydrostatic bearing in a turbocharger is engine lubrication oil. Engine oil is supplied to the center housing of the turbocharger, passes over the bearings, and drains through an opening, typically at the bottom of the center housing of the turbocharger. The oil typically returns back into the crankcase of the engine.
In some engine applications, factors such as high oil flow rates into the center housing of the turbocharger, steep angles of engine and vehicle operation, or sub-optimal oil passage routing, may create oil pooling in the center housing resulting from poor drainage of oil out of the center housing. Oil pooling in the center housing of the turbine may cause an increase in pressure of the air, and therefore the oil, inside the center housing that may, in turn, cause leakage of oil past the oil seals around the shaft and between the center housing and the turbine or compressor housings.
Accordingly, there is a need for better pressure management in the center housings of turbochargers that may experience poor oil drainage during operation.